Comparison of Minority Carrier Lifetime Measurements in Superstrate and Substrate CdTe PV Devices: Preprint

We discuss typical and alternative procedures to analyze time-resolved photoluminescence (TRPL) measurements of minority carrier lifetime (MCL) with the hope of enhancing our understanding of how this technique may be used to better analyze CdTe photovoltaic (PV) device functionality. Historically, TRPL measurements of the fast recombination rate (t1) have provided insightful correlation with broad device functionality. However, we have more recently found that t1 does not correlate as well with smaller changes in device performance, nor does it correlate well with performance differences observed between superstrate and substrate CdTe PV devices. This study presents TRPL data for both superstrate and substrate CdTe devices where both t1 and the slower TRPL decay (t2) are analyzed. The study shows that changes in performance expected from small changes in device processing may correlate better with t2. Numerical modeling further suggests that, for devices that are expected to have similar drift field in the depletion region, effects of changes in bulk MCL and interface recombination should be more pronounced in t2. Although this technique may provide future guidance to improving CdS/CdTe device performance, it is often difficult to extract statistically precise values for t2, and therefore t2 data may demonstrate significant scatter when correlated with performance parameters

DLTS investigations on CIGS solar cells from an inline co-evaporation system with RbF post-deposition treatment

In this study, Deep Level Transient Spectroscopy (DLTS) measurements have been performed on Cu(In,Ga)Se$_{2}$ (CIGS) solar cells from an inline co-evaporation system. The focus of this investigation is directed on the effect of rubidium-fluoride (RbF)-post-deposition treatment (PDT) on the defects in the CIGS absorber layer. Different traps can be identified and their properties are calculated. Herein, different methods of evaluations have been used to verify the results. Specifically, one minority trap around 400 meV was found to show a significant reduction of the trap density due to the alkali treatment. In contrast, a majority trap at approximately 600 meV is unaffected

Fingerprints Indicating Superior Properties of Internal Interfaces in Cu(In,Ga)Se2 Thin-Film Solar Cells

Growth of Cu(In,Ga)Se2 (CIGS) absorbers under Cu-poor conditions gives rise to incorporation of numerous defects into the bulk, whereas the same absorber grown under Cu-rich conditions leads to a stoichiometric bulk with minimum defects. This suggests that CIGS absorbers grown under Cu-rich conditions are more suitable for solar cell applications. However, the CIGS solar cell devices with record efficiencies have all been fabricated under Cu-poor conditions, despite the expectations. Therefore, in the present work, both Cu-poor and Cu-rich CIGS cells are investigated, and the superior properties of the internal interfaces of the Cu-poor CIGS cells, such as the p-n junction and grain boundaries, which always makes them the record-efficiency devices, are shown. More precisely, by employing a correlative microscopy approach, the typical fingerprints for superior properties of internal interfaces necessary for maintaining a lower recombination activity in the cell is discovered. These are a Cu-depleted and Cd-enriched CIGS absorber surface, near the p-n junction, as well as a negative Cu factor (∆β) and high Na content (>1.5 at%) at the grain boundaries. Thus, this work provides key factors governing the device performance (efficiency), which can be considered in the design of next-generation solar cells

Final report on Assessment of the candidate Projects of Energy Community Interest (PECI) and Projects for Mutual Interest (PMI)

A REKK és a DNV GL konzorciuma a 2013-as első PECI lista kiválasztásában nyújtott tanácsadó munkája után 2016-ban is támogatást nyújtott a második PECI lista kiválasztáshoz. A konzorcium kialakított egy projekt értékelési módszertant, majd az elfogadott módszertan alapján értékelte a benyújtott infrastruktúra projekteket. Az értékelés egy előzetes vizsgálatból és egy modellezési és indikátor számítási szakaszból állt. Az előzetes értékelés során megvizsgáltuk, hogy a benyújtott projektek megfelelnek-e a 347/2013 EU rendelet Energy Community által adoptált változatában szereplő általános és specifikus kritériumoknak, illetve a benyújtott projektadatokat verifikáltuk. Az előzetes kritériumoknak megfelelt 31 projektet (12 villamos energia hálózati és 17 gázhálózati és 1 olaj infrastruktúra) értékeltük. A villamosenergia és gázhálózati infrastruktúra projektek esetében a módszertan két lépésen alapult. Első lépésben a modellezésen alapuló költség haszon vizsgálatát végeztük el a projekteknek és kiszámítottuk a társadalmi nettó jelenértékét. Ez az indikátor szerepelt az elemzésben a legnagyobb súllyal (60%). Második lépésben a nem monetizálható hasznok esetében további indikátorok (a rendszerbiztonság, a projektek előrehaladottsága, a piaci versenyhez elősegítése, stb.) kerültek kialakításra, az indikátorok 1-5 skálán pontokat kaptak és a súlyokkal beszorozva megkaptuk minden egyes projekt összpontszámát. Az ily módon sorrendbe állítható projektlista és a részletes érzékenységvizsgálatok eredménye alapján hozta meg a tagállamok képviselőiből álló csoport a döntését az előzetes PECI/PMI listáról

Investigation of the Effect of I-ZnO Window Layer on the Device Performance of the Cd-Free CIGS Based Solar Cells: Preprint

This paper focuses on preparing Cd-free, CIGS-based solar cells with intrinsic high resistivity ZnO (I-ZnO) films deposited by metal-organic chemical vapor deposition (MOCVD) technique at different deposition substrate temperature and I-ZnO film thickness, and the effect of the prior treatment of CIGS films by ammonium hydroxide (NH4OH) diluted solution on the device performance

DISPERSION MODELING FOR REGULATORY APPLICATIONS by

Air qual ity sim u la tion mod els are ex ten sively used in as sess ing the im pacts of com bus tion plants. A wide va ri ety of mod els are avail able. In or der to rec om mend the most ap pro pri ate air qual ity mod el ing tech nique that should be in cor po rated into a stan dard reg u la tory frame work in the Re pub-lic of Mac e do nia the per for mances of three Gaussi an-plume at mo spheric dis per sion mod els, ADMS 3, OML, and ISCST3 have been ana lysed. The mod els have been tested against the ground level mea sure ments of the daily mean SO2 con cen tra tions ob tained at the four lo ca tions around the Ther mal Power Plant of Bitola. Two ex per i men tal cam paigns have been per formed. The three model re sults and the mea sure ments at the pre sented lo ca tions for 365 days in the year are com pared. An anal y sis of the ob tained re sults is pre sented in the pa per as well. The me te o ro log i cal pre pro cessor MADAM_MP has been used to pro vide the re quired bound ary layer pa ram e ters for es ti ma tion of the trans port and dif fu sion of pol lut ants re leased from the stacks. Us ing the MADAM_MP a year of hourly val ues for the mix ing height, Monin-Obukhov length, sur face fric tion ve loc ity, sen si ble heat flux, and Pasquill's sta bil ity class, have been cal cu lated from the avail able me te o ro log i cal data set. The ap proach and the main equa tions for the bound ary layer pa ram e ters es ti ma tion are pre-sented in this pa per

Application of inverse concepts to drying

This pa per deals with the ap pli ca tion of in verse ap proaches to es ti ma tion of dry ing body pa ram e ters. Si mul ta neous es ti ma tion of the thermophysical prop er ties of a dry ing body as well as the heat and mass trans fer co ef fi-cients, by us ing only tem per a ture mea sure ments, is ana lysed. A math e mat i-cal model of the dry ing pro cess has been de vel oped, where the mois ture con tent and tem per a ture fields in the dry ing body are ex pressed by a sys tem of two cou pled par tial dif fer en tial equa tions. For the es ti ma tion of the un-known pa ram e ters, the tran sient read ings of a sin gle tem per a ture sen sor lo-cated in an in fi nite flat plate, ex posed to con vec tive dry ing, have been used. The Levenberg-Marquardt method and a hy brid op ti mi za tion method of minimization of the least-squares norm are used to solve the pres ent pa ram-e ter es ti ma tion prob lem. An anal y sis of the in flu ence of the dry ing air ve loc-ity, dry ing air tem per a ture, dry ing body di men sion, and dry ing time on the thermophysical prop er ties es ti ma tion, that en ables the de sign of the proper ex per i ments by us ing the so-called D-op ti mum cri te rion was con ducted. In or der to per form this anal y sis, the sen si tiv ity co ef fi cients and the sen si tiv ity ma trix de ter mi nant were cal cu lated for the char ac ter is tic dry ing re gimes and the dry ing body di men sions. Key words: inverse approach, drying, thermophysical properties, heat and mass transfer coefficient